The invention resides in the technical fields of immunology and medicine.
Alzheimer""s disease (AD) is a progressive disease resulting in senile dementia. See generally Selkoe, TINS 16, 403-409 (1993); Hardy et al., WO 92/13069; Selkoe, J. Neuropathol. Exp. Neurol. 53, 438-447 (1994); Duff et al., Nature 373, 476-477 (1995); Games et al., Nature 373, 523 (1995). Broadly speaking the disease falls into two categories: late onset, which occurs in old age (65+ years) and early onset, which develops well before the senile period, i.e, between 35 and 60 years. In both types of disease, the pathology is the same but the abnormalities tend to be more severe and widespread in cases beginning at an earlier age. The disease is characterized by two types of lesions in the brain, senile plaques and neurofibrillary tangles. Senile plaques are areas of disorganized neuropil up to 150 xcexcm across with extracellular amyloid deposits at the center visible by microscopic analysis of sections of brain tissue. Neurofibrillary tangles are intracellular deposits of tau protein consisting of two filaments twisted about each other in pairs.
The principal constituent of the plaques is a peptide termed Axcex2 or xcex2-amyloid peptide. Axcex2 peptide is an internal fragment of 39-43 amino acids of a precursor protein termed amyloid precursor protein (APP). Several mutations within the APP protein have been correlated with the presence of Alzheimer""s disease. See, e.g., Goate et al., Nature 349, 704) (1991) (valine717 to isoleucine); Chartier Harlan et al. Nature 353, 844 (1991)) (valine717 to glycine); Murrell et al. , Science 254, 97 (1991) (valine717 to phenylalanine); Mullan et al., Nature Genet. 1, 345 (1992) (a double mutation changing lysine595-methionine596  to asparagine595-leucine596). Such mutations are thought to cause Alzheimer""s disease by increased or altered processing of APP to Axcex2, particularly processing of APP to increased amounts of the long form of Axcex2 (i.e., Axcex21-42 and Axcex21-43). Mutations in other genes, such as the presenilin genes, PS1 and PS2, are thought indirectly to affect processing of APP to generate increased amounts of long form Axcex2 (see Hardy, TINS 20, 154 (1997)). These observations indicate that Axcex2, and particularly its long form, is a causative element in Alzheimer""s disease.
McMichael, EP 526,511, proposes administration of homeopathic dosages (less than or equal to 10xe2x88x922 mg/day) of Axcex2 to patients with preestablished AD. In a typical human with about 5 liters of plasma, even the upper limit of this dosage would be expected to generate a concentration of no more than 2 pg/ml. The normal concentration of Axcex2 in human plasma is typically in the range of 50-200 pg/ml (Seubert et al., Nature 359, 325-327 (1992)). Because EP 526,511""s proposed dosage would barely alter the level of endogenous circulating Axcex2 and because EP 526,511 does not recommend use of an adjuvant, it seems implausible that any therapeutic benefit would result.
By contrast, the present invention is directed inter alia to treatment of Alzheimer""s and other amyloidogenic diseases by administration of Axcex2 or other immunogen to a patient under conditions that generate a beneficial immune response in the patient. The invention thus fulfills a longstanding need for therapeutic regimes for preventing or ameliorating the neuropathology of Alzheimer""s disease.
In one aspect, the invention provides methods of preventing or treating a disease characterized by amyloid deposition in a patient. Such methods entail inducing an immune response against a peptide component of an amyloid deposit in the patient. Such induction can be active by administration of an immunogen or passive by administration of an antibody or an active fragment or derivative of the antibody. In some patients, the amyloid deposit is aggregated Axcex2 peptide and the disease is Alzheimer""s disease. In some methods, the patient is asymptomatic. In some methods, the patient is under 50 years of age. In some methods, the patient has inherited risk factors indicating susceptibility to Alzheimer""s disease. Such risk factors include variant alleles in presenilin gene PS1 or PS2 and variant forms of APP. In other methods, the patient has no known risk factors for Alzheimer""s disease.
For treatment of patients suffering from Alzheimer""s disease, one treatment regime entails administering a dose of Axcex2 peptide to the patient to induce the immune response. In some methods, the Axcex2 peptide is administered with an adjuvant that enhances the immune response to the Axcex2 peptide. In some methods, the adjuvant is alum. In some methods, the adjuvant is MPL. The dose of Axcex2 peptide administered to the patient is typically at least 1 or 10 xcexcg, if administered with adjuvant, and at least 50 xcexcg if administered without adjuvant. In some methods, the dose is at least 100 xcexcg.
In some methods, the Axcex2 peptide is Axcex21-42. In some methods, the Axcex2 peptide is administered in aggregated form. In other methods, the Axcex2 peptide is administered in dissociated form. In some methods, the therapeutic agent is an effective dose of a nucleic acid encoding Axcex2 or an active fragment or derivative thereof. The nucleic acid encoding Axcex2 or fragment thereof is expressed in the patient to produce Axcex2 or the active fragment thereof, which induces the immune response. In some such methods, the nucleic acid is administered through the skin, optionally via a patch. In some methods, a therapeutic agent is identified by screening a library of compounds to identify a compound reactive with antibodies to Axcex2, and administering the compound to the patient to induce the immune response.
In some methods, the immune response is directed to aggregated Axcex2 peptide without being directed to dissociated Axcex2 peptide. For example, the immune response can comprise antibodies that bind to aggregated Axcex2 peptide without binding to dissociated Axcex2 peptide. In some methods, the immune response comprises T-cells that bind to Axcex2 complexed with MCH1 or MHCII on CD8 or CD4 cells. In other methods, the immune response is induced by administering an antibody to Axcex2 to the patient. In some methods, the immune response is induced by removing T-cells from the patient, contacting the T-cells with Axcex2 peptide under conditions in which the T-cells are primed, and replacing the T-cells in the patient.
The therapeutic agent is typically administered orally, intranasally, intradermally, subcutaneously, intramuscularly, topically or intravenously. In some methods, the patient is monitored followed administration to assess the immune response. If the monitoring indicates a reduction of the immune response over time, the patient can be given one or more further doses of the agent.
In another aspect, the invention provides pharmaceutical compositions comprising Axcex2 and an excipient suitable for oral and other routes of administration. The invention also provides pharmaceutical compositions comprising an agent effective to induce an immunogenic response against Axcex2 in a patient, and a pharmaceutically acceptable adjuvant. In some such compositions, the agent is Axcex2 or an active fragment thereof. In some compositions, the adjuvant comprises alum.
In some compositions, the adjuvant comprises an oil-in-water emulsion. In some compositions, the Axcex2 or active fragment is a component of a polylactide polyglycolide copolymer (PLPG) or other particle. The invention further provides compositions comprising Axcex2 or an active fragment linked to a conjugate molecule that promotes delivery of Axcex2 to the bloodstream of a patient and/or promotes an immune response against Axcex2. For example, the conjugate can serve to promote an immune response against Axcex2. In some compositions, the conjugate is cholera toxin. In some compositions, the conjugate is an immunoglobulin. In some compositions, the conjugate is attenuated diphtheria toxin CRM 197 (Gupta, Vaccine 15, 1341-3 (1997).
The invention also provides pharmaceutical compositions comprising an agent effect to induce an immunogenic response against Axcex2 in a patient with the proviso that the composition is free of Complete Freund""s adjuvant. The invention also provides compositions comprising a viral vector encoding Axcex2 or a an active fragment thereof effective to induce an immune response against Axcex2. Suitable viral vectors include herpes, adenovirus, adenoassociated virus, a retrovirus, sindbis, semiliki forest virus, vaccinia or avian pox.
The invention further provides methods of preventing or treating Alzheimer""s disease. In such methods, an effective dose of Axcex2 peptide is administered to a patient. The invention further provides for the use of Axcex2, or an antibody thereto, in the manufacture of a medicament for prevention or treatment of Alzheimer""s disease.
In another aspect, the invention provides methods of assessing efficacy of an Alzheimer""s treatment method in a patient. In these methods, a baseline amount of antibody specific for Axcex2 peptide is determined in a tissue sample from the patient before treatment with an agent. An amount of antibody specific for Axcex2 peptide in the tissue sample from the patient after treatment with the agent is compared to the baseline amount of Axcex2 peptide-specific antibody. An amount of Axcex2 peptide-specific antibody measured after the treatment that is significantly greater than the baseline amount of Axcex2 peptide-specific antibody indicates a positive treatment outcome.
In others methods of assessing efficacy of an Alzheimer""s treatment method in a patient, a baseline amount of antibody specific for Axcex2 peptide in a tissue sample from a patient before treatment with an agent is determined. An amount of antibody specific for Axcex2 peptide in the tissue sample from the subject after treatment with the agent is compared to the baseline amount of xcex2 peptide-specific antibody. A reduction or lack of significant difference between the amount of Axcex2 peptide-specific antibody measured after the treatment compared to the baseline amount of Axcex2 peptide-specific antibody indicates a negative treatment outcome.
In other methods of assessing efficacy of an Alzheimer""s disease treatment method in a patient a control amount of antibody specific for Axcex2 peptide is determined in tissue samples from a control population. An amount of antibody specific for Axcex2 peptide in a tissue sample from the patient after administering an agent is compared to the control amount of Axcex2 peptide-specific antibody. An amount of Axcex2 peptide-specific antibody measured after the treatment that is significantly greater than the control amount of Axcex2 peptide-specific antibody indicates a positive treatment outcome.
In other methods of assessing efficacy of an Alzheimer""s treatment method in a patient, a control amount of antibody specific for Axcex2 peptide in tissues samples from a control population is determined. An amount of antibody specific for Axcex2 peptide in a tissue sample from the patient after administering an agent is compared to the control amount of Axcex2 peptide-specific antibody. A lack of significant difference between the amount of Axcex2 peptide-specific antibody measured after beginning said treatment compared to the control amount of Axcex2 peptide-specific antibody indicates a negative treatment outcome.
Other methods of monitoring Alzheimer""s disease or susceptibility thereto in a patient, comprise detecting an immune response against Axcex2 peptide in a sample from the patient. In some such methods, the patient is being administered an agent effective to treat or prevent Alzheimer""s disease, and the level of the response determines the future treatment regime of the patient.
In other methods of assessing efficacy of an Alzheimer""s treatment method in a patient a value for an amount of antibody specific for Axcex2 peptide in tissue sample from a patient who has been treated with an agent is determined. The value is compared with a control value determined from a population of patient experiencing amelioriation of, or freedom from, symptoms of Alzheimer""s disease due to treatment with the agent. A value in the patient at least equal to the control value indicates a positive response to treatment.
The invention further provides diagnostic kits for performing the above methods. Such kits typically include a reagent that specifically binds to antibodies to Axcex2 or which stimulates proliferation of T-cells reactive with Axcex2.